1. Field of the Invention
The invention relates to a trench lining device (lining box) consisting of a base box of lining plates, kept apart by braces, which have a blunt edge, in particular a square pressure cross beam, which is relatively stable against blows of an excavator bucket, on their upper edge, and on the underside of each lining plate a cutting edge for forcing the base box downward into the ground, and with at least one tier of lining plates of a raised box arranged aligned on the base box.
2. Description of the Related Art
A device for shoring trench walls with at least two support walls of wall sections disposed on top of each other is described in DE 20 57 263 C3. The walls are kept at a distance from each other with the aid of cross braces. The lower pair of support walls ("base box" for simplicity) has a cutting edge at the lower edge, which is intended to be driven into the ground, while the upper edge of the plate located opposite the cutting edge is embodied as a blunt edge, for example as a square pressure cross beam. The raised boxes, which are intended to be arranged in tiers above the base box of plates in essentially a vertically aligned manner and which consist of pairs of plates, have a blunt (straight or slightly arched) end profile or the previously mentioned blunt edge, on both the upper and the lower edges. i.e. no cutting edge. The lining plates of the raised boxes essentially differ from the lining plates of the base boxes only by a cutting edge being provided or not. The cutting edge makes it possible to press the base box into the ground. The raised box does not require this cutting edge because it rests on the base box, which has already cut the soil to the width of the trench.
The essential disadvantage when using special raised elements or boxes lies in that they are only used for raising, that is only with relatively deep trenches. The base box is always needed in contrast to this. The raised box only in rare cases, but then at least one raised box is needed for every base box. Therefore the building contractor is required to keep approximately as many raised boxes as base boxed in storage if he is to be prepared to fill orders flexibly, even though the raised boxes are not even required at normal trench depths.